private static void OnKeyDownHandler()

in src/Calculator/Common/KeyboardShortcuManager.cs [638:708]
57 lines of code
22 McCabe index (conditional complexity)

            private static void OnKeyDownHandler(CoreWindow sender, KeyEventArgs args)
            {
                if (args.Handled)
                {
                    return;
                }

                var key = args.VirtualKey;
                int viewId = Utilities.GetWindowId();

                bool isControlKeyPressed = (Window.Current.CoreWindow.GetKeyState(Windows.System.VirtualKey.Control) & CoreVirtualKeyStates.Down) == CoreVirtualKeyStates.Down;
                bool isShiftKeyPressed = (Window.Current.CoreWindow.GetKeyState(Windows.System.VirtualKey.Shift) & CoreVirtualKeyStates.Down) == CoreVirtualKeyStates.Down;
                bool isAltKeyPressed = (Window.Current.CoreWindow.GetKeyState(Windows.System.VirtualKey.Menu) & CoreVirtualKeyStates.Down) == CoreVirtualKeyStates.Down;

                // Handle Ctrl + E for DateCalculator
                if ((key == Windows.System.VirtualKey.E) && isControlKeyPressed && !isShiftKeyPressed && !isAltKeyPressed)
                {
                    NavigateModeByShortcut(isControlKeyPressed, isShiftKeyPressed, false, key, ViewMode.Date);
                    return;
                }

                if (s_ignoreNextEscape.TryGetValue(viewId, out var currentIgnoreNextEscape))
                {
                    if (currentIgnoreNextEscape && key == Windows.System.VirtualKey.Escape)
                    {
                        if (s_keepIgnoringEscape.TryGetValue(viewId, out var currentKeepIgnoringEscape))
                        {
                            if (!currentKeepIgnoringEscape)
                            {
                                HonorEscape();
                            }
                            return;
                        }
                    }
                }

                if (s_fHonorShortcuts.TryGetValue(viewId, out var currentHonorShortcuts))
                {
                    if (currentHonorShortcuts)
                    {
                        var myVirtualKey = key;
                        var lookupMap = GetCurrentKeyDictionary(isControlKeyPressed, isShiftKeyPressed, isAltKeyPressed);
                        if (lookupMap == null)
                        {
                            return;
                        }

                        var buttons = EqualRange(lookupMap, (MyVirtualKey)myVirtualKey);
                        if (buttons.Count() <= 0)
                        {
                            return;
                        }

                        KeyboardShortcutManagerLocals.RunFirstEnabledButtonCommand(buttons);

                        // Ctrl+C and Ctrl+V shifts focus to some button because of which enter doesn't work after copy/paste. So don't shift focus if Ctrl+C or Ctrl+V
                        // is pressed. When drop down is open, pressing escape shifts focus to clear button. So dont's shift focus if drop down is open. Ctrl+Insert is
                        // equivalent to Ctrl+C and Shift+Insert is equivalent to Ctrl+V
                        //var currentIsDropDownOpen = s_IsDropDownOpen.find(viewId);
                        if (!s_IsDropDownOpen.TryGetValue(viewId, out var currentIsDropDownOpen) || !currentIsDropDownOpen)
                        {
                            // Do not Light Up Buttons when Ctrl+C, Ctrl+V, Ctrl+Insert or Shift+Insert is pressed
                            if (!(isControlKeyPressed && (key == Windows.System.VirtualKey.C || key == Windows.System.VirtualKey.V || key == Windows.System.VirtualKey.Insert))
                                & !(isShiftKeyPressed && (key == Windows.System.VirtualKey.Insert)))
                            {
                                KeyboardShortcutManagerLocals.LightUpButtons(buttons);
                            }
                        }
                    }
                }
            }